1. Field of Invention
The present invention relates to a concrete measuring and mixing apparatus which allows the operator to selectively vary the composition of the concrete mix at the job site. More specifically, the present invention relates to a concrete mixing apparatus, detachably mounted on a standard truck frame, which takes sand, cement, gravel, and water and mixes them in desired proportions at the job site to produce small batches of concrete of a desired composition, when needed.
2. Description of the Prior Art
The use of a common type of concrete mixing truck has a disadvantage in that the truck can only be used for simultaneous mixing and transport of large amounts of ready-mixed concrete. It does not meter various quantities of cement, gravel, sand, and water in optionally variable proportions at the job site. Thus, the distance between the mixing site and the job site must be taken into account to allow for setting of the concrete. When the truck contains more than the amount of concrete needed at a given job site the rest must be poured relatively quickly, often as waste. Also, an extensive stationary batch plant for metering the concrete materials is necessary.
Another type of concrete mixing apparatus is shown in U.S. Pat. No. 3,746,313 to Weeks et al. The mixing apparatus of this patent mixes separate amounts of cement, sand, gravel, and water to produce concrete at the job site as does the present invention. However, many features of the prior art mixing apparatus render it ineffective for commerical use. The apparatus of this prior art patent was unbalanced, and therefore unstable on the highway. The mixing drum in this apparatus was ineffective and subject to clogging. The conveyors in this patent would wear fast and were also subject to clogging. The mechanical drive was delicate and developed insufficient force to overcome binding. And most importantly, the metering slide of this prior art patent would stick and lock up with cement when damp. However, these problems have been corrected by the invention of the present application.